1. Field of the Invention
The present invention relates to a light source control apparatus, a control method for controlling the same, and a liquid crystal display apparatus.
2. Description of the Related Art
A method is known, in which the luminance of the light source of a backlight is variably controlled partially or for the entire screen in accordance with the contents of an input video signal (picture signal) in order to expand the contrast of a liquid crystal display. A backlight control method, in which the light source luminance provided at a position corresponding to each of a plurality of divided areas set in a display area of a display panel is variably controlled depending on a statistical amount (gradation value) of an image to be displayed on the divided area, is generally referred to as “local dimming”. The control method for the local dimming is roughly classified into a control method in which only the light source luminance of the dark area is lowered, and a control method in which the light source luminance of the dark area is lowered and the light source luminance of the bright area is raised depending on the amount of decrease in the light source luminance of the dark area. In this context, when the light source luminance of the dark area is lowered and the light source luminance of the bright area is raised as in the latter control method, the electric power consumption is also temporally fluctuated increasingly or decreasingly with respect to the average value in accordance with the dynamic change of the light source luminance. Therefore, in view of the protection of a power source circuit which supplies the electric power to the light source of the backlight, a technique has been suggested, in which the light source luminance is controlled while making the restriction or limitation so that the electric power consumption of the light source does not exceed the electric power amount capable of being supplied by the power source.
For example, JP2010-152174A suggests that a luminance correction coefficient, which allows an average light source luminance of the entire screen to be not more than a certain prescribed value, is calculated for each of frames, and the luminance correction coefficient is used to correct the light source luminance of the entire backlight. According to JP2010-152174A, the electric power consumption can be suppressed in temporal average in relation to 1 frame.
On the other hand, JP2001-312241A suggests such a technique that a plurality of light sources for constructing a backlight are successively turned ON every certain delay times, and thus the instantaneous concentration of the electric power load is suppressed. According to JP2001-312241A, the plurality of light sources are successively turned ON every certain delay times, and hence the electric power load can be dispersed within a period of 1 frame when the luminances of the respective light sources are identical with each other.